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EN
The interaction of an intense laser pulse with a solid target produces large number of fast free electrons. This emission gives rise to two distinct sources of the electromagnetic pulse (EMP): the pulsed return current through the holder of the target and the out flow of electrons into the vacuum. A relation between the characteristics of laser-produced plasma, the target return current and the EMP emission are presented in the case of a massive Au target irradiated with the intensity of up to 3 × 1016 W/cm2. The emission of the EMP was recorded using a 12 cm diameter Moebius loop antennas, and the target return current was measured using a new type of inductive target probe (T-probe). The simultaneous use of the inductive target probe and the Moebius loop antenna represents a new useful way of diagnosing the laser–matter interaction, which was employed to distinguish between laser-generated ion sources driven by low and high contrast laser pulses.
EN
Proton acceleration from laser-generated plasma is carried out at intensities ranging between 1010 and 1019 W/cm2, by using ns, ps and fs laser systems. The high energy density transferred from the pulsed laser beam into the solid target generates ionized species released in vacuum from the solid surface. Fast electrons followed by slower ions build up a double-layer and a consequent electric field, which is responsible for the ion acceleration mainly along the target-normal. Polymeric targets containing nanostructures (or metallic species) with high laser absorbing capacity, and metallic hydrates (or H-enriched metals), permit to increase the plasma temperature and density, thus to improve the proton beam energy and current. Thick targets and low laser intensities, operating in repetitive pulse, allows to generate high currents of low energy protons. On the other hand, through the use of thin targets and high laser intensities enabled the generation of high proton energies, above 1 MeV.
EN
Multi-MeV proton and light ion beams had been produced using the 300 ps, kJ-class iodine laser, operating at Prague Asterix Laser System (PALS) Centre in Prague. The target material had been chosen in such a way so as to increase the proton beam current density (approaching 0.1 A/cm2 at the distance of 1 m from the source). The real-time ion detection was performed by means of a standard flat and ring ion collectors (IC) in the time-of-flight (TOF) configuration. The ICs had been shielded with aluminum foils of various thickness, in order to cut the long photo-peak contribution that is usually overlapping with the ultrafast particle signal, and to analyze mainly the laser-accelerated proton beam. The processing of the obtained experimental IC data is described in some detail, including the deconvolution of TOF signals, evaluation of the UV/soft-X-ray photo-peak absorption, and ion transmission calculations for different metallic filters.
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